This invention relates generally to the field of alignment and particularly to the field of highly accurate alignment of two bodies relative to each other.
Aligning two bodies relative to each other has been a problem in many fields for years. Numerous mechanical approaches too voluminous to describe here have been developed to permit accurate alignment of two or more bodies. Such mechanical approaches have proved successful to a greater or lesser extent but suffer from only being able to achieve accuracy to the extent typically achievable by mechanical approaches. For extremely precise applications, however, such mechanical approaches do not provide sufficient accuracy.
To improve alignment accuracy, optical systems have been developed such as the "Visual Alignment Aid" described in NASA TECH BRIEF NO. 75-10228. This device consists of a beam splitting-combining cube with orthogonally oriented roof prisms cemented to two adjacent faces of the beam splitting-combining cube. Each roof prism independently inverts one of the reflected/transmitted beams produced within the cube during a first optical pass therethrough. The beams are recombined in the cube and exit a face different from the entrance face to the cube.
The NASA developed device is useful for alignment of telescopes and the like. Such alignment can be determined by the fact that the light rays exiting the device are parallel to each other only if the entering rays enter perpendicular to the entrance face. Accordingly, two images can be viewed if the entering rays do not enter perpendicular to the entrance face.
While the foregoing approach is useful in aligning telescopes and in other applications, it is not as suitable for use where the light source is a polarized light source such as a gas laser. This is due to the fact that the beams, when split, are not, in general, split into beams having substantially the same intensity. Consequently, when the beams are recombined, the composite beam is not simply a sum of the two split beams but a more complex function of them. As such, the NASA device is not readily useable for alignment when polarized light is being transmitted.
A further difficulty associated with the alignment device described above is that it utilizes roof prisms. In order to achieve the results as described in the NASA TECH BRIEF, the 90.degree. dihedral angles of these prisms must be made with great precision otherwise the beams exiting the device will not have the proper alignment required to achieve its objective with a high degree of accuracy. While achieving the degree of precision necessary to make the device accurately operative is well within the skill of the art, nevertheless, manufacturing such prisms with the required precision is costly thereby significantly adding to the overall manufacturing cost of the device.
In view of the foregoing difficulties with the closest known prior art, it is the principal objective of the invention to provide a passive compensator for use in optical alignment which compensates for both angular and translational misalignment of a polarized beam.
It is still a further objective of the invention to provide an alignment system which includes a compensator for passively compensating for angular and translational misalignment in the system produced by a polarized light source, such as a laser, utilized in the system itself.
It is yet a further objective of the invention, in its most preferred form, to provide a passive compensator for compensating for angular and translational misalignment of a polarized beam where the compensator utilizes optical elements that do not have to be manufactured to high precision tolerances thereby reducing the overall cost of the system as compared to comparable ones utilizing high precision tolerance optical elements.